The alveolar macrophage (AM) and the polymorphonuclear leukocyte (PMN) are prime defenders of the human lung against infection. The goal of this research is to further define the role of these phagocytes in patients with unexplained recurrent pulmonary infections. Techniques have been developed in our laboratory to measure the quantitative bactericidal and metabolic capacity of the human PMN. These techniques are designed to stress the maximum reserve of the PMN by employing increasing bacteria to neutrophil ratios and graded concentrations of a chemical stimulant, phorbol myristate acetate (PMA). The ability of these methods to uncover defects of quantitative neutrophil function has clarified the pathogenesis of the infections in many of these patients in which PMN function was normal by conventional testing. This proposal seeks to adapt our quantitative bactericidal and biochemical techniques to study the function of AM obtained by bronchial washings from patients with recurrent pulmonary infections. PMN and macrophages from monocyte transformation will be studied when possible in these same patients. AM from rabbits will be used when appropriate. Evaluation of both PMN and AM function in the same patient will delineate isolated from generalized defects in cellular host-defense. Improvement in the understanding of the metabolism and bactericidal ability of the AM and PMN in these patients will clarify the pathogenesis of their infections, increase diagnostic accuracy, and provide more specific and effective treatment.